The broad and long-term objective of this research project is to use, develop and market an instrument for the simultaneous recording of sympathetic nerve activity (SNA) and electrocardiogram (ECG) using electrodes on the skin. This method (neuECG) was discovered in Dr. Chen's research laboratory at the Krannert Institute of Cardiology, and a patent application has been filed by Indiana University. Arrhythmotech LLC was developed to further advance this concept and we propose that neuECG has a significant commercial value by providing a new non-invasive tool for arrhythmia prediction and detection. Sympathetic tone is important in cardiac arrhythmogenesis. Heart rate variability analyses and microneurography recordings are standard techniques to assess sympathetic tone. However, these techniques have multiple limitations. The neuECG was developed to record ECG and nerve activity simultaneously on the skin of human subjects. In collaboration with Dr. Chen's lab, we have obtained strong preliminary results in human patients to document the successful recording of neuECG in normal volunteers and in patients with postoperative atrial fibrillation and electrical storm. In these preliminary studies, neuECG recording showed electrical signals consistent with SNA, and that the SNA correlated with heart rate acceleration, atrial fibrillation and ventricular arrhythmias. We propose that the neuECG may serve as a new diagnostic tool for the prediction of cardiac arrhythmias and sudden cardiac death. In addition, it may be helpful in the diagnosis of diseases involving the peripheral nervous system, such as neuromuscular diseases. In this Phase 1 application, we have designed two clinical studies to document the feasibility and utility of neuECG recording in normal volunteers and in patients with cardiac arrhythmias. Once this is complete, we will immediately apply for Phase 2 funding to commercialize the neuECG for human use. Specific Aim 1: To record simultaneous ECG and SNA in normal volunteers and correlate the nerve activity to heart rate. We will consent normal volunteers for this study. We will place ECG electrodes on the skin using standard limb lead and chest lead configurations. The signals are digitized and filtered to record ECG and SNA simultaneously. After baseline recordings, the patients will undergo 2-min cold water immersion test, followed by Valsalva maneuver. The data will be analyzed to test the hypothesis that it is feasible to simultaneously record SNA from the skin, and that SNA recordings correlate with heart rate acceleration in normal volunteers. Specific Aim 2: To record simultaneous ECG and SNA in patients with cardiac arrhythmias and correlate an increase in nerve activity to arrhythmia onset. We will perform continuous neuECG recording at the bedside in patients with recurrent cardiac arrhythmias. The data will be analyzed to determine if the SNA are present on the skin of the diseased patients, and if the SNA correlates with the onset of cardiac arrhythmias. The results will be used to test the hypothesis that a continuous neuECG recording is feasible in patients with heart diseases, and that SNA predicts the impending onset of cardiac arrhythmias.